Attenuator for very high frequency waves



April 10, 1951 T E 2,548,] 16

ATTENUATOR FOR VERY HIGH FREQUENCY WAVES Filed Jan. 19, 1950 I)? venzar fifrbr/ fiwzya jflfafare 5 Patented Apr. 10, 1951 'ATTENUATOR FOR VERY HIGH FREQUENCY WAVES Herbert Francois Matar, Vaucresson, France, assignor to 'Societe Anonyme dite Compagnie des Freins & Signaux Westinghouse, Paris,

France Application January 19, 1950, Serial No. 139,431 In France February 1, 1949 Y 3 Claims. 1 1

This invention relates to. attenuators, more particularly to attenuators for very high and ultra-high frequency radio waves. By very high frequency waves it is intended-in this specification to designate the wave-length range of from one to ten decimeters, and by ultra-high frequency waves, the wave-length range of from one to ten centimeters.

It. is often desirable to adjust in. an accurately controllable manner the power output of a high frequency oscillation-generator, and it is an object of this inventionto provide for this purpose animproved attenuatorparticularly designed for use-in connection with very high andultra-high wave frequencies which is very simple to con;

struct and operate, and which is reduced in size. Another object'i's to provide suchi'anattenuator which is capable of accurately adjusting a:power output within a'range extendingfrom a predetermined maximum value downtoa value'in the order of about 10-1 or WattsL r r xAnother object-is to provide such an attenua tor which is particularly simple in" that no special in its axial position by an annular insulating means are provided in it to prevent impedance:

mismatching effects, while remaining highlyemcient in operation.

A further object isto provide such an attenua tor with means'for varying. the input energy as desired, and with means for immediately reading the value of the thus-adjusted input energy;

The 'above and further objects and advantages of theinvention are achieved by providing an" attenuator of the type specified which comprises a high-frequency input guide tube with a central rod therein, the outer end of said guide being pin [2 being rigid with, and projecting outwardlyj from, an insulating .ring support I3 through which extendsand to whichis secured the piston connected with thehigh frequency generator and 1 the inner endcarrying a fixed' coupling' element, and an output guide tube arranged in coaxial alignment with the input guide also having a central rod' therein,- and having its outer end connected with a receiver apparatus and its inner end carrying a movable coupling element adjustably displaceable relatively to the fixed input coupling element. The fixed coupling element of the input guide is connected with a short-circuiting means for adjustment of the power input into the device. Further said fixed input coupling element carries a crystal or diode rectifier connected in series with the short-circuiting means and which acts as a probe element for measuring the input energy.

The invention will now be described in greater detail with reference to the accompanying diagrammatic drawing, which illustrates by way of indication and not of limitation cross-section 'Trolitul or, the like.

ll a slider I9 is displaceable which one preferred embodiment "of an attenuator, for very-high and ultra-high frequency waves according to the invention; :As shown, the attenuator comprises a high-frequency input guide or tube l axially of which is supported a rod 2 the outer end of-which may be connected through any appropriate connectingmeans as by the plugsocket shown with a high-frequencyoscillationgeneratorfand the inner end of whichcarries a fixed coupling piston 3. The rod 2 is supported block or ring 4 which may be made of polystyrene such as known on themarket under the trade mark nTrolitul? or the, like; In coaxial alignment with the inputguidel is disposed an output guide or tube; 5 axially of which is supporteda rod 6 havingits outer end connectable through any suitable connector device as with the plug-socket shown with a load or receiver for the attenuated high frequency energy and which at its inner end supports for sliding movement relatively to said rod; 6,;5;the= piston-rod l of a; movable; coupling piston B- carried'in. a position adjacent to, and

adjustably-spaced-from, the input coupling piston 3. The rod 6 is supported in the output guide 5 by aninsulating ring 9 -made of polystyrene such as knownon the market under. the trade-mark For .axial positional adjustment of the movable piston 8 an actuating bushing I0 is used formed with an internal helical, groove ll, into which a pin l2 projects, the

I'Od='l5.0f piston 8. The bushing 10 is movable in rotation but is prevented from axial. movement,

by. means of an abutment flange I l around the output guide 5. As shown, the output guide 5 is formedwith a longitudinal slot or groove l5 through its wall to allow the actuating pin l2 to. extend therethroughl. It is to be observed that this slot I 5 is at all times sealed by the surrounding bushing l0 so that there is no risk of outside dirt penetrating through the slot into the guide 5.

Between'the input 'and'output wave guides l and 5 and extending'generally perpendicularly thereto is a tube member l6 axially of which is disposed a rod I! which is connected with the fixed or input coupling piston 3. The tube I6 is retained in position relatively to the guides I and 5 by any suitably-designed means. Over the rod provides the short-circuitingmeans serving to adjust the input energy into the attenuator. Displacementof theslider I9 is efijected by means of a rotatable actuating bushing 20 surrounding the tube It, through the medium of a pin 2| projecting at one end thereof into an inner helical groove 22 of the bushing 29 and secured at its other end to the shorting'jmember [9. The tube It is of course formed with a slot 23 through its wall for passage of the pin 2|, and this slot is at all times sealed by the surrounding bushing 20. Suitable abutment means such as the nut l8 engaging a threaded end portion of the rod H are provided to prevent axial displacement of the rotatable bushing 20.

In order to fix the energy level of the highfrequency input energy, thereby to be assured of the fact that, in two successive measurements effected with a device connected with the output of the attenuator the input energy remains the same, it is necessary to be able to measure said input energy. For this purpose according to the invention a measuring probe member. is used comprising a crystal rectifier or diode 24 one terminal of which is imbedded in the fixed coupling piston 3' and the other terminal for instance in threaded engagement as shown With a ole-couplingelement 25 housed in a tube member 26 secured in any suitable way to the input and output tubes l and 5 'on the side opposite that at which the tube member 16. is supported. Thus it may be seen that the rectifier 2A is in series with the .short-circuiting means l|--l 9.

The decoupling element 25 is'mountedon the rod 2G in a readily removablemanner in order to enable it to be replaced bya similar element of different diameter depending on the particular range of wavelengths in connection withwhich the attenuator is to be used. For this purpose the element 25 is shown as retained in position by means of an internally threaded bushing or cap 21 screwed over the externally threaded endot'the tube member 26; with the interp'osal of an insulating washer 28 of Trolitul or the'like. A socket 29 rigid with the decoupling element 25 is provided for plugging connection with a suitable measuring instrument.

I The attenuator assembly just described makes it possible to adjust the power transmitted therethroughover a range extending from a predetermined maximum down to a value of about or 10 watt by varying the spacing from the movable piston 8 to the fixed piston 3. Ac cording to the invention, the desired attenuating action is produced by the setting up of vibratory energy in the mode E0 within the guide land absorbing a greater or less amount of said energy depending on the adjusted spacing between the movable output and fixed input couplingpistons 8 and 3.

It will be noted from the foregoing description that in the device shown no particular means are providedfor averting impedance-mismatchment shock efiects, and no special load resistances are included, as a result of which an extremely simple attenuator construction is achieved. Experience has shown that the absence of such means while affording great simplicity at the same time does not detract from the operating efiiciency of the attenuator of the invention, as the defects due to mismatched impedance are greatly reduced as the amount of power transmitted through the attenuator is itself reduced, to such an extent that when for instance the spacing adjustment.

in-the device is 1 centimeter, the impedance mismatchment shock efiect already has a negligible .value. y

An important advantage of'the attenuator described is the possibility of adjusting the input energy to any desired value by actuating the short-circuiting member l'l-I9, said value of the input energy being at all times ascertainable owing to the rectifier or probe member 24. Thus any high-frequency oscillation-generator may be applied to the attenuator and the input energy may be adjusted With the short-circuiting means I'I-l9 to any desired value as indicated by the measuring instrument plugged in at 29.

By way of indication, the operating wavelength range of the above-described attenuator is from about 20 centimeters to about 3 centimeters. It will be understood of course that many modifications may be made in the details of the exemplary device illustrated and described within the purview of the ensuing claims. Thus among other possible variations, the actuating means for producing the adjusting displacements of the movable piston 8 and the shortcircuiting member. or slider I9 may be provided in forms other than those shown. The mounting for the rectifier or probe member 24 may also difier from that illustrated.

What I claim is:

1. In an attenuator in combination an input and an output wave-guide in coaxial alignment and in energy-transmitting relationship with each other at their inner ends, an axial rod through the input guide and a telescopable axial rod through the output guide, means at the outer ends of each of said rods cooperating with the adjacent ends of the related guides for connection thereof with an energy-transmitting and receiving means respectively, a fixed input coupling element at the inner end of said first rod and an outputcoupling element at the inner end of said telescopable rod movable towards and away from said input coupling element for transmitting a variable fraction of the available amount of input energy on said input coupling element, adjustable short-circuiting means in series with said input coupling element for varying said available amount of input, energy thereon, a rectifier member connected at one end with said input coupling element and a de-coupling means connected with the other end of said rectifier, and an indicating instrument connected with said de-coupling means.

2. Attenuator as in claim 1 wherein said decoupling element is interchangeable and removably secured to the outer end of said rectifier.

3. In an attenuator in combination an input and an output guide in axial alignment and in energy-transmittin relationship at their inner ends with each other, an energy-transmitting space defined at the inner ends of said guides, a pair of tubes extending in opposite directions from said space normally to said guides, a fixed axial rod through the input guide and a slidable axial rod through said output guide, connector means at the outer ends of said respective rods cooperating with the adjacent ends of the related guides for connection with an energy-transmitting and receiving means respectively, a fixed input coupling element at the inner end of said input guide in said space and an output coupling element at the inner end of said output guide and means for adjustin said slidable rod in axial position to move said output towards and away from said input coupling element to transmit a desiredfraction of the amount of input energy available on said input coupling element to said output coupling element, short-circuiting means for abstracting a variable amount of input energy from said input coupling element to leave only a desired amount of available input energy thereon, said short-circuiting means comprising a rod connected to said input coupling element and extending axially through one of said pair of tubes, a short-circuiting slider slidable on said rod and adjusting means for adjusting said slider in axial position on said rod, and means for indicating the said available amount of energy on said input coupling element, said indicating means comprising a rectifier connected at its inner end with said input coupling element and extending therefrom through the other one of said further tubes axially thereof, a replaceable de-coupling element in said other tube removably connected 15 at its inner end with the other end of said rectifier, and means for plugging an indicating instrument to the outer end of said de-coupling element.

HERBERT FRANooIs MATARE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,411,553 Ramo Nov. 26, 1946 2,497,094 Moreno Feb. 14, 1950 2514,54 1 Hansen July 11, 1950 

